Deploying an application

Now that we have successfully configured Argo CD on our cluster, let's deploy an application. To demonstrate the difference between a GitOps-based delivery approach and traditional deployment methods, we'll migrate the UI component of our sample application from using the kubectl apply -k approach to an Argo CD-managed deployment.

An Argo CD application is a Custom Resource Definition (CRD) that represents a deployed application instance in an environment. It defines key information such as the application name, Git repository location, and path to the Kubernetes manifests. The application resource also specifies the desired state, target revision, sync policy, and health check policy.

First, let's remove the existing sample application from the cluster:

~$kubectl delete namespace -l app.kubernetes.io/created-by=eks-workshop

namespace "carts" deleted

namespace "catalog" deleted

namespace "checkout" deleted

namespace "orders" deleted

namespace "other" deleted

namespace "ui" deleted

Now we'll populate our Git repository with a simple Helm chart:

~/environment/eks-workshop/modules/automation/gitops/argocd/Chart.yaml

apiVersion: v2
name: retail-store-sample-chart
description: A Helm chart for the AWS retail store ui component
type: application
version: 0.0.1
dependencies:
  - name: retail-store-sample-ui-chart
    alias: ui
    version: 1.2.1
    repository: oci://public.ecr.aws/aws-containers

This chart wraps the published chart for the UI component by using it as a Helm dependency.

Let's copy this file to our Git directory:

~$mkdir -p ~/environment/argocd/ui

~$cp ~/environment/eks-workshop/modules/automation/gitops/argocd/Chart.yaml \

~/environment/argocd/ui

Our Git directory should now have this structure:

~$tree ~/environment/argocd

`-- ui

    `-- Chart.yaml

Now we'll push our configuration to the Git repository:

~$git -C ~/environment/argocd add .

~$git -C ~/environment/argocd commit -am "Adding the UI service"

~$git -C ~/environment/argocd push

Next, let's create an Argo CD Application configured to use our Git repository:

~$argocd app create ui --repo $GITOPS_REPO_URL_ARGOCD \

--path ui --dest-server https://kubernetes.default.svc \

--dest-namespace ui --sync-option CreateNamespace=true

application 'ui' created

We can verify that the application has been created:

~$argocd app list

NAME         CLUSTER                         NAMESPACE  PROJECT  STATUS     HEALTH   SYNCPOLICY  CONDITIONS

argocd/ui    https://kubernetes.default.svc  ui         default  OutOfSync  Missing  Manual      <none>

This application is now visible in the Argo CD UI:

Alternatively, we can also interact with Argo CD objects directly using the kubectl command:

~$kubectl get applications.argoproj.io -n argocd

NAME   SYNC STATUS   HEALTH STATUS

apps   OutOfSync     Missing

If you open the Argo CD UI and navigate to the apps application, you'll see:

In Argo CD, "out of sync" indicates that the desired state defined in your Git repository doesn't match the actual state in your Kubernetes cluster. Although Argo CD is capable of automated synchronization, for now we'll manually trigger this process:

~$argocd app sync ui

~$argocd app wait ui --timeout 120

After a short period, the application should reach the Synced state, with all resources deployed. The UI should look like this:

This confirms that Argo CD has successfully installed the Helm chart and it's now in sync with the cluster.

We've now successfully migrated the UI component to be deployed using Argo CD. Any future changes pushed to the Git repository will be automatically reconciled to our EKS cluster.

To verify that all resources related to the UI service are deployed, run the following commands:

~$kubectl get deployment -n ui ui

NAME   READY   UP-TO-DATE   AVAILABLE   AGE

ui     1/1     1            1           61s

~$kubectl get pod -n ui

NAME                 READY   STATUS   RESTARTS   AGE

ui-6d5bb7b95-rjfxd   1/1     Running  0          62s